|Appearance||Dark gray cubic crystals|
|Structure||Formula weight||144.64 amu|
|Lattice constant||0.56533 nm|
|State of matter at STP||solid|
|Melting point at SP||1513 K|
|Boiling point at SP||?|
|Band gap at 300K||1.424 eV|
|Electron effective mass||0.0067 me|
|Light hole effective mass||0.082 me|
|Heavy hole effective mass||0.45 me|
|Electron mobility at 300 K||0.92 m2/V·s|
|Hole mobility at 300 K||0.04 m2/V·s||Precautions|
|Decompostion products||Highly toxic arsenic fumes||SI units were used where possible.|
Gallium arsenide (GaAs) is a chemical compound composed of gallium and arsenic. It is an important semiconductor, and is used to make devices such as microwave frequency integrated circuits, infrared light-emitting diodes and laser diodes.
The electronic properties of GaAs are superior to silicon's. It has a higher saturated electron velocity and higher electron mobility, allowing it to function at frequencies in excess of 250 GHz. Also, GaAs devices generate less noise than silicon devices.
Another advantage of GaAs is that it has a direct bandgap. This means that it can be used to emit light. Silicon has an indirect bandgap, and so is very poor at emitting light. (Nonetheless, recent advances may make silicon LEDs and lasers possible).
Silicon has two major advantages over GaAs. First, silicon is cheap. This is for several reasons: silicon's large wafer size (maximum of ~300mm compared to ~150mm diameter), high strength allowing for easier processing, and of course the scale of the economy.
The second major advantage is the existence of silicon dioxide—one of the best known insulators of any kind. Silicon dioxide can easily be incorporated into silicon circuits wherever a good insulator is required. GaAs circuits must either use the intrinsic semiconductor itself or silicon nitride; neither comes close to the extremely good properties of silicon dioxide.